Patent Literature 1 and Patent Literature 2 disclose apparatuses to perform thermal treatment of a substrate such as a semiconductor wafer utilizing induction heating. As illustrated in FIG. 5, in the thermal treatment apparatus disclosed in Patent Literature 1 being a batch type thermal treatment apparatus, wafers 2 stacked in multiple stages are put into a crystal process tube 3, a heating tower 4 which is formed with an electrically-conductive member such as graphite is placed at the outer circumference of the process tube 3, and a solenoid-like induction heating coil 5 is arranged at the outer circumference thereof. According to the thermal treatment apparatus 1 having the abovementioned structure, the heating tower 4 is heated owing to an influence of magnetic flux generated by the induction heating coil 5 and the wafers 2 placed in the process tube 3 is heated by radiation heat from the heating tower 4.
Further, as illustrated in FIG. 6, in the thermal treatment apparatus disclosed in Patent Literature 2 being a sheet type thermal treatment apparatus, concentrically hyper-fractionated susceptors 7 are formed of graphite or the like, wafers 8 are placed at the upper face side of the susceptors 7, and a plurality of circular induction heating coils 9 are placed at the lower face side on a concentric circle. Here, power control can be performed separately against the plurality of induction heating coils 9. According to the thermal treatment apparatus 6 having the abovementioned structure, since heat transfer between a susceptor 7 located in a heating range of each induction heating coil 9 and another susceptor 7 heated by another induction heating coil 9 is suppressed, controllability of temperature distribution of the wafers 8 due to power control against the induction heating coils 9 is improved.
Further, Patent Literature 2 discloses that heat distribution is appropriately controlled by fractionating the susceptors 7 on which the wafers 8 are placed. Patent Literature 3 discloses that heat distribution is improved with devising of a sectional shape of a susceptor. According to a thermal treatment apparatus disclosed in Patent Literature 3, through consideration that a heat generation amount becomes small at the inner side having small diameter of a circularly-formed induction heating coil, increase of the heat generation amount and increase of thermal capacity are to be achieved as causing a distance to an inner side part from the induction heating coil to be shorter than that to an outer side part by enlarging thickness at the inner side part of the susceptor.